1. Field of the Invention
The present invention relates to cleaning units, process cartridges, and electrophotographic image-forming apparatuses.
2. Description of the Related Art
Electrophotographic image-forming apparatuses form images on recording media by an electrophotographic image-forming process. Examples of electrophotographic image-forming apparatuses include electrophotographic copiers, electrophotographic printers (e.g., LED printers and laser beam printers), electrophotographic facsimile machines, and multifunction devices having such functions.
Conventional electrophotographic image-forming apparatuses include process cartridges detachable from the main bodies thereof. These cartridges integrally include an electrophotographic photosensitive member and process units that act thereon. This type of cartridge allows users to perform maintenance of the apparatuses without the assistance of servicepersons, thus greatly improving ease of operation. As a result of their convenience, process cartridges are widely used in electrophotographic image-forming apparatuses.
Process cartridges include a cleaning unit for cleaning a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as a process unit. The cleaning unit is held by a cartridge frame. The cleaning unit has a cleaning member for recovering toner remaining on the circumferential surface of the photosensitive drum. Examples of the cleaning member include webs, fur brushes, rollers, and blades.
Among the aforementioned, blades are most frequently used. An elastic blade is used to scrape residual toner off the surface of the photosensitive drum by bringing an edge of the blade into contact with the surface of the photosensitive drum. On the other hand, a disadvantage of using a cleaning member in the form of a web, a fur brush, or a roller is that it tends to involve a large cleaning unit for structural reasons.
An example of prior art is taught in U.S. Pat. No. 5,608,509, in which a metal sheet supports an elastic blade. This metal sheet is bent to achieve rigidity characteristics so that it can withstand a reaction force applied to the elastic blade from a photosensitive drum. The metal sheet is fixed to a cartridge frame with a screw; therefore, a space for the metal sheet and the screw is required.
In another example of prior art taught in Japanese Patent Laid-Open No. 4-295 877, a cleaning blade is integrally formed with a metal shaft so as to cover the metal shaft . Here, however, the cleaning blade can sag in the middle because the metal shaft is supported only at the longitudinal ends thereof.
It would be desirable to provide a cleaning unit which overcomes the aforementioned disadvantages of the prior art.